Among conventional power conversion apparatuses such as inverters and converters, there is a power conversion apparatus that includes power semiconductor modules each containing power semiconductor devices, and a cooler for cooling the power semiconductor modules. In such power semiconductor modules, heat generated in the power semiconductor devices during conduction needs to be released to outside via heat releasing fins, and the key point here is the structure design for improving heat releasing properties within a size limit.
For example, in a power conversion apparatus disclosed in PTL 1, semiconductor modules and cooling tubes are alternately stacked to form a unit. The stack unit is then sandwiched by a holding plate and a plate spring member from the outside, so that the cooling tubes are brought into contact with the semiconductor modules. With the use of the holding plate and the plate spring member, however, the stack unit becomes large in size, and it is difficult to reduce the size of the power conversion apparatus. Moreover, this will lead to an increase in costs.
In a power conversion apparatus disclosed in PTL 2, a semiconductor circuit unit including semiconductor devices is housed in a cylindrical case, and the semiconductor circuit unit is bonded to the inner wall (the heat releasing member) of the case via an insulating member for securing electrical insulation. In this structure, the thinner portions around the heat releasing member spring back away from the semiconductor circuit unit. As a result, tensile stress is generated in the semiconductor circuit unit, and the insulating member might be detached from the inner wall of the case. The detachment of the bonding portion degrades the heat releasing properties of the semiconductor devices, and will lead to damage of the power semiconductors.